Existing flat planar appearing ceiling fans are the most popular type of ceiling fans sold in the United States, and are known to have relatively poor air moving performance at different operating speeds. See for example U.S. Pat. Des. 355,027 to Young and Des. 382,636 to Yang. These patents while moving air are not concerned with maximizing optimum downward airflow.
Additionally, many of the flat ceiling fan blades have problems such as wobbling, and excessive noise that is noticeable to persons in the vicinity of the fan blades. The flat planar rectangular blade can have a slight tilt to increase air flow but are still poor in air moving performance, and continue to have the other problems mentioned above.
Aircraft, marine and automobile engine propeller type blades have been altered over the years to shapes other than flat rectangular. See for example, U.S. Pat. Nos. 1,903,823 to Lougheed; 1,942,688 to Davis; 2,283,956 to Smith; 2,345,047 to Houghton; 2,450,440 to Mills; 4,197,057 to Hayashi; 4,325,675 to Gallot et al.; 4,411,598 to Okada; 4,416,434 to Thibert; 4,730,985 to Rothman et al. 4,794,633 to Hickey; 4,844,698 to Gornstein; 5,114,313 to Vorus; and 5,253,979 to Fradenburgh et al.; Australian Patent 19,987 to Eather.
However, these patents are generally used for high speed water, aircraft, and automobile applications where the propellers are run at high revolutions per minute (rpm) generally in excess of 500 rpm. None of these propellers are designed for optimum airflow at low speeds of less than approximately 200 rpm which is the desired speeds used in overhead ceiling fan systems.
Some alternative blade shapes have been proposed for other types of fans. See for example, U.S. Pat. Nos. 1,506,937 to Miller; 2,682,925 to Wosik; 4,892,460 to Volk; 5,244,349 to Wang; Great Britain Patent 676,406 to Spencer; and PCT Application No. WO 92/07192.
Miller '937 requires that their blades have root “lips 26” FIG. 1 that overlap one another, and would not be practical or useable for three or more fan blade operation for a ceiling fan. Wosik '925 describes “fan blades . . . particularly adapted to fan blades on top of cooling towers such for example as are used in oil refineries and in other industries . . . ”, column 1, lines 1-5, and does not describe any use for ceiling fan applications.
The Volk '460 patent by claiming to be “aerodynamically designed” requires one curved piece to be attached at one end to a conventional planar rectangular blade. Using two pieces for each blade adds extreme costs in both the manufacturing and assembly of the ceiling itself. Furthermore, the grooved connection point in the Volk devices would appear to be susceptible to separating and causing a hazard to anyone or any property beneath the ceiling fan itself. Such an added device also has necessarily less than optimal aerodynamic properties.
Tilted type design blades have also been proposed over the years. See for example, U.S. Pat. No. D451,997 to Schwartz.
However, none of the prior art modifies design shaped blades to optimize twist angles to optimize energy consumption and airflow, and reduce wobble and noise problems.
The inventors and assignee of the subject invention have been at the forefront of inventing high efficiency ceiling fans by using novel twisted blade configurations. See for example, U.S. Pat. Nos. 6,884,034 and 6,659,721 and 6,039,541 to Parker et al.
However, these fans have unique and to some a futuristic appearance as compared to traditional flat planar fan blades. Although, highly efficient, some consumers may tend to prefer the traditional flat planar blades that have been widely used as compared to the high efficiency ceiling fans that use twisted blades.
Thus, the need exists for better performing traditionally appearing ceiling fan blades over the prior art.